The objective was to evaluate the effect of feeding oxidized corn oil with or without a dietary antioxidant (AOX) on performance, tissue oxidative status, and meat quality in barrows. One hundred sixty barrows were arranged in a 2 × 2 factorial of treatments in a complete randomized block design with 8 pens per treatment and 5 pigs per pen. Diets contained 5.0 mg/kg of 1 of 2 types of corn oil (fresh or oxidized) with or without antioxidant. Final oxidized oil was produced in a heated container by continuously bubbling air heated to 95°C at a rate of 80 L/min to reach a target peroxide value of approximately 150 and 7.5 mEq/kg in the final diet. After 56 d, barrows fed diets formulated with fresh oil had increased ADG (P = 0.03) and ADFI (P = 0.04) and heavier final BW (P = 0.03) than barrows fed oxidized oil. Increased G:F (P = 0.07) was observed for barrows fed diets with AOX after 28 d of feeding but not after 56 d of feeding (P = 0.67) when compared with barrows not fed AOX. An increase (P = 0.06) in plasma thiobarbituric acid reactive substances (TBARS) values, a decrease (P = 0.03) in plasma glutathione peroxidase (GPx) enzyme activity, and a decrease (P = 0.01) in liver vitamin E concentrations were observed in barrows fed diets with oxidized oil. Dietary AOX reduced plasma protein carbonyl content regardless of oil type (P = 0.04). Barrows fed fresh oil had 4.4% heavier HCW (P = 0.01) and 0.7 percentage units increase in dressing percentage (P = 0.01) compared with barrows fed oxidized oil. Loin TBARS values from barrows fed AOX were lower (P < 0.001) after 14 and 21 d of storage in both fresh and oxidized oil groups. In summary, oxidized oil impaired growth performance and caused oxidation stress. Dietary AOX partially ameliorated the negative effects of oxidized oil in finishing pigs by reducing protein oxidation and improving shelf life.

The objective of this experiment was to determine if increasing lysine in the diets of immunologically castrated (IC) male pigs would increase percentage fat free lean and carcass cutting yields when compared with physical castrates. The anti-gonadotropin-releasing factor (GnRF) immunological product (Improvest, Pfizer Animal Health) is used worldwide to immunologically castrate entire male pigs to control boar taint and take advantage of the inherent ability of the entire male to deposit more muscle, less fat, and grow more efficiently than physically castrated males. The immunization process essentially allows the pig to grow as an entire male pig for most of its life and then removes any boar odor (boar taint) before slaughter. Reported lean meat advantages may also provide economic benefits to the domestic meat industry. Approximately 1,200 male pigs [physical castrates, IC males, and entire males] were each assigned to 1 of 4 diet programs which differed in lysine content. In each case, lysine was fed in a conventional step-down program that culminated with the following concentrations in the late finishing diet: physical castrates fed low lysine (0.7%), IC fed low lysine (0.7%), IC fed low/medium lysine (0.8%), IC fed medium/high lysine (0.9%), IC fed high lysine (1.0%), and entire males fed high lysine (1.0%). At 25 wk of age (5 wk post-second injection), pigs were individually weighed and the 2 pigs (n=96) in each pen closest to the median pig BW were selected and slaughtered. The right side of each carcass was dissected into soft tissue, skin, and bone. Proximate composition was determined on the soft tissue to determine percentage fat-free lean. The left side of each carcass was weighed and initially fabricated into ham, loin, belly, and whole shoulder. Each primal piece was weighed again and further fabricated into respective subprimal cuts. Immunological castration did not change (P>0.05) shear force values or ultimate pH when compared with either physical castrates or entire males. Marbling appeared to decrease as dietary lysine was increased among IC males. As expected, IC males had a greater (P<0.05) percentage fat-free lean than physical castrates but less (P<0.05) than entire males. Immunologically castrated males fed diets with medium/high and high lysine had greater (P<0.05) lean cutting yields and carcass cutting yields than physical castrates. Lean cutting yield and carcass cutting yields appeared to increase as dietary lysine was increased among IC males. Overall, immunological castration improved carcass cutability, increased percentage fat free lean, and had no effect on pork quality when compared with physical castrates.

No abstract

The objective was to investigate the effect of various doses and durations of ractopamine hydrochloride (RAC) on pig HCW, cutting yields, and meat quality. Late-finishing pigs (approximately 93 kg) were allotted to 12 treatments 35 d before slaughter. Treatments consisted of negative control (NEG; 13.1% CP, 0.64 TID Lys), positive control (POS; 17.8% CP, 0.94 TID Lys), and 2 RAC doses (5 and 7.4 mg/kg) with 5 different feeding durations for each dose (7, 14, 21, 28, or 35 d). Pigs on ractopamine-duration diets were fed NEG until incorporation of RAC, and then the diet was switched to POS to comply with label requirements. A subset of 240 pigs was utilized to determine the effects of RAC on carcass cutting yields. This subset was selected by taking the 5 pigs closest to the average pen weight from 4 complete replicates. Differences in response to RAC between 5 and 7.4 mg/kg were not significant. Therefore, RAC dosages were pooled, resulting in an average dose of 6.2 mg/kg, which was then compared with NEG and POS diets. Ractopamine increased (P < 0.05) HCW by 2.5 and 2.3 kg compared with the NEG and POS diets, respectively. Hot carcass weight also increased linearly (P=0.003) as RAC duration increased. Indicators of carcass leanness increased with RAC compared with NEG. Estimated carcass lean percentage increased (P=0.010) 1 percentage unit from 54.79 to 55.79%, carcass cut yield increased (P<0.001) 1.23 percentage units from 50.61 to 51.84%, and (P=0.006) boneless lean cut yield increased 1.27 percentage units from 36.71 to 37.98%. Ractopamine decreased (P=0.002) subjective marbling scores 0.49 units from the NEG value of 3.0, but RAC did not differ (P=0.203) from POS. Subjective color values and shear force aging curves for RAC were not significantly different from NEG or POS. Overall, RAC had greater responses in carcass weight and cut yield than NEG, and had minimal effects on meat quality.

Selection of breeding stock is a crucial step in any breeding program, therefore the methodology for animal evaluation has evolved rapidly and in recent decades has incorporated the use of molecular markers. Several multinational companies have made available to producers commercial tests based on these technologies, which allow assessing the predisposition of animals to express a specific phenotype. However, some doubts have begun to arise about negative effects of improper use of molecular markers, these are problems associated with inbreeding depression and long-term loss of response to selection. Therefore, the objective of this study was to assess allele and genotype frequencies of 4 polymorphisms associated with marbling in 7 beef cattle breeds being present in La Araucanía Region of Chile. We evaluated leptin, thyroglobulin, DGAT1 and FABP4 genes, which showed different frequency distributions among breeds with higher allele frequency for marbling in Aberdeen Angus breed and a low frequency in Belgian Blue and Hereford breeds. We conclude that it is feasible to use these tools in genetic programs, but it is also necessary to have reliable genealogical records and advice of professional or technical institutions that can integrate genotypic information from molecular markers in prediction models used for selection of breeding stock. Palabras clave: criterio de selección, marcadores moleculares, BLUP. INTRODUCCIÓN La selección de los reproductores de la siguiente gene-ración es un paso fundamental en todo programa de mejora genética. Para realizar esta selección, el mejorador debe utilizar el valor genético aditivo de los individuos, dejando para reposición aquellos animales cuya combinación de genes es la mejor para el carácter de interés. El objetivo de esta selección es maximizar la ganancia genética por generación mediante un correcto ordenamiento por mérito genético de los candidatos a ser reproductores (Buxade 1995). La genética ha dedicado un continuo esfuerzo a la obtención, a partir de la información fenotípica de un individuo y la de sus parientes, de un predictor del valor genético que se libere de los efectos ambientales y posea propiedades estadísticas óptimas (Buxade 1995). De esta manera, la metodología para la evaluación de los animales ha evolucionado rápidamente, y en las últimas décadas se ha pasado desde aquellas técnicas que consideraban tan solo parte de la información genealógica, mediante índices de selección (Smith 1936, Hazel 1943, Henderson 1990), a otras más sofisticadas que emplean toda la información (genealogía, sexo, raza, predio, variables productivas, etc.) mediante la metodología BLUP (Best Linear Unbiased Predictor) propuesta por Henderson (1949). De forma paralela, durante la segunda mitad del siglo XX los progresos realizados en biología molecular permitieron importantes avances en la identificación de las variaciones genéticas que se producen a nivel de la secuencia del ADN. La actividad ganadera no ha estado al margen de dichos avances y grandes multinacionales como P...